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This upstream patch addresses CVE-2014-3517 and is tracked under
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Launchpad bug 1325128. It is addressed in the Juno trunk, Icehouse
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2014.1.2, and Havana 2013.2.4. It has been modified to apply cleanly
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into our current Havana implementation
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commit 1dd97d1335f6ec028d0e4440250f80802a2f1d18
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Author: Grant Murphy <[email protected]>
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Date: Tue Jul 8 03:35:40 2014 +0000
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Avoid possible timing attack in metadata api
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Introduce a constant time comparison function to
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nova utils for comparing authentication tokens.
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Conflicts:
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nova/tests/test_utils.py
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nova/utils.py
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Closes-bug: #1325128
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Change-Id: I7374f2edc6f03c7da59cf73ae91a87147e53d0de
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(cherry picked from commit 9f59ca751f1a392ef24d8ab73a7bf5ce9655017e)
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diff --git a/nova/api/metadata/handler.py b/nova/api/metadata/handler.py
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index 50387ab..74bb4f7 100644
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--- a/nova/api/metadata/handler.py
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+++ b/nova/api/metadata/handler.py
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@@ -31,6 +31,7 @@ from nova import exception
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from nova.openstack.common.gettextutils import _
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from nova.openstack.common import log as logging
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from nova.openstack.common import memorycache
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+from nova import utils
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from nova import wsgi
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CACHE_EXPIRATION = 15 # in seconds
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@@ -172,7 +173,7 @@ class MetadataRequestHandler(wsgi.Application):
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instance_id,
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hashlib.sha256).hexdigest()
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- if expected_signature != signature:
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+ if not utils.constant_time_compare(expected_signature, signature):
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if instance_id:
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LOG.warn(_('X-Instance-ID-Signature: %(signature)s does not '
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'match the expected value: %(expected_signature)s '
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diff --git a/nova/tests/test_utils.py b/nova/tests/test_utils.py
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index b38ea50..820fe09 100644
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--- a/nova/tests/test_utils.py
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+++ b/nova/tests/test_utils.py
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@@ -1083,3 +1083,10 @@ class GetImageFromSystemMetadataTestCase(test.NoDBTestCase):
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# Verify that the foo1 key has not been inherited
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self.assertTrue("foo1" not in image)
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+
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+
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+class ConstantTimeCompareTestCase(test.NoDBTestCase):
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+ def test_constant_time_compare(self):
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+ self.assertTrue(utils.constant_time_compare("abcd1234", "abcd1234"))
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+ self.assertFalse(utils.constant_time_compare("abcd1234", "a"))
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+ self.assertFalse(utils.constant_time_compare("abcd1234", "ABCD234"))
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diff --git a/nova/utils.py b/nova/utils.py
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index 4757f3a..5f10a8a 100755
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--- nova-2013.2.3/nova/utils.py.~2~ 2014-09-02 13:57:46.030039835 -0700
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+++ nova-2013.2.3/nova/utils.py 2014-09-02 13:57:49.391998275 -0700
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@@ -23,6 +23,7 @@ import contextlib
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import datetime
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import functools
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import hashlib
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+import hmac
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import inspect
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import os
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import pyclbr
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@@ -1288,3 +1289,20 @@ def get_boolean(value):
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return value
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else:
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return strutils.bool_from_string(value)
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+
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+if hasattr(hmac, 'compare_digest'):
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+ constant_time_compare = hmac.compare_digest
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+else:
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+ def constant_time_compare(first, second):
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+ """Returns True if both string inputs are equal, otherwise False.
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+
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+ This function should take a constant amount of time regardless of
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+ how many characters in the strings match.
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+
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+ """
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+ if len(first) != len(second):
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+ return False
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+ result = 0
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+ for x, y in zip(first, second):
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+ result |= ord(x) ^ ord(y)
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+ return result == 0
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